单词	triangular numbers
释义	triangular numbers plural noun : the successive sums n(n + 1)/2 where n = 1, 2, 3, … of the first n natural numbers 1, 3, 6, 10, 15, … representable by dots arranged in triangles Word History First Known Use 1795, in the meaning defined above
随便看	heritors heritresses heritrices heritrix heritrixes heriz herizes Herkimer herky-jerky herl captaining captainly captainry captains captains general captainship captainships captan captans captation captcha caption caption code captioned captioner

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